The relationship between in vitro digestible cell wall and the cell-wall content of forage

Abstract

SUMMARYIn oven-dried whole plants from three regrowths of four varieties of Panicum maximum, leaf and stem of normal and stunted oats at three stages of first growth, leaf and stem of rape and the whole plant of millet, cell wall ranged from 14 to 77% of the organic matter. In vitro digestible cell wall ranged from 13 to 46% of the organic matter and was closely related to the cell wall (residual standard deviation, ± 2·5). In 16 legume hays the average in vitro digestible cell wall was 22·1% of the forage organic matter compared with an average value of 20·5% found previously from in vivo digestibility experiments with legumes. An unsatisfactory feature of the in vitro digestibility determination was that in silages and low quality grass hays, the digestible cell wall was low relative to known in vivo values for these forage types. The separate determinations of cell wall and in vitro digestible cell wall would add to the confidence that can be placed on estimates of in vivo digestibility from laboratory measurements. Often, the determination of cell-wall content is sufficient for this purpose.